1. Field of the Invention
This invention relates to dye-forming charge-sensitive recording materials. One aspect of the invention relates to the use of (A) a dye-forming coupler, and (B) an image-forming combination in a charge-sensitive recording material which is capable of producing a dye image and silver image by dry development processes.
2. Description of the State of the Art
A variety of recording materials and processes have been proposed to provide image recording. The better known and commercially more successful of these recording materials and processes can be classified as photographic, thermographic or electrographic or as a combination of two or more of these processes. For example, one known recording material is a photothermographic material which is a heat developable photosensitive material. Each of the known image recording materials and processes have certain advantages for particular uses. However, the materials and processes also suffer from disadvantages which limit the usefulness in particular applications. For example, conventional photographic materials have the disadvantage that they are not room light handleable prior to imagewise exposure and processing. Thermographic materials require imagewise heating to provide a visible image and are not capable of the degree of light sensitivity provided by conventional photographic materials. Electrographic materials including, for example, xerographic materials require mechanical dust pattern transfer procedures to provide a desired image.
It has been desirable to provide an image recording material and process which enable the formation of a dye image and a silver image under daylight conditions, yet avoid the need for conventional processing baths and solutions.
Heat developable photographic materials which after imagewise exposure can be heated to produce a developed image in the absence of processing solutions or baths are known. These photosensitive materials have the disadvantage that they are not room light handleable prior to imagewise exposure for recording purposes.
Another means proposed for imaging involves a recording material which produces an image by passing an electric current through the recording material. Such recording materials involve electrographic image recording techniques. One such recording material comprises a conventional light-sensitive photographic material that is positioned contiguous to a photoconductive layer for image recording purposes. Upon applying a uniform electric field across the photoconductive and photographic layers and simultaneously imagewise exposing the photoconductive layer to a light pattern, an imagewise current flow is produced in the photographic layer. This imagewise current flow is produced in the photographic layer. This imagewise current flow, in turn, produces a developable latent image in the photographic layer. The recording material, however, has the disadvantages associated with light-sensitive photographic materials which require processing with conventional solutions and baths. Moreover, the material requires a substantial current flow in the recording layer and therefore provides a relatively lengthy exposure time with low current flow or a high current flow with a short exposure time.
Dry electrographic recording materials and processes which involve production of a visible image in a charge-sensitive recording element have been described in, for example, French Pat. No. 2,280,517, published Feb. 27, 1976, and U.S. Pat. No. 4,113,484. Such dry electrographic recording materials can be processed by dry development techniques. However, no suggestion is given of producing a dye image and silver image in such a recording material and process.
Accordingly, a continuing need has existed to provide an electrically activatable recording element that (a) avoids the need for conventional processing solutions and baths, (b) enables room light handling of the recording material prior to imagewise exposure and processing, and (c) enables the formation of a dye image and silver image, preferably a dye image that enhances the silver image.